THE METACARPU8. 165 



UNCIFORM (Fig. 113). 

 The Unciform (uncus, a hook ; forma, likeness) may be readily distinguished 



For os magnum. 

 For cuneiform. 



For fourth meta- 

 tarsal. 



Unciform process. ^^ For fifth 



metatarsal. 



FIG. 113. The loft unciform. 



by its wedge-shaped form and the hook-like process that projects from its palmar- 

 surface. It is situated at the inner and lower angle of the carpus, with its base 

 downward, resting on the two inner metacarpal bones, and its apex directed 

 upward and outward. The superior surface, the apex of the wedge, is narrow, 

 convex, smooth, and articulates with the semilunar. The inferior surface articu- 

 lates with the fourth and fifth metacarpal bones, the concave surface for each 

 being separated by a ridge which runs from before backward. The posterior or 

 dorsal surface is triangular and rough, for ligamentous attachment. The anterior 

 or palmar surface presents, at its lower and inner side, a curved, hook-like pro- 

 cess of bone, the unciform process, directed from the palmar surface forward and 

 outward. It gives attachment by its apex to the annular ligament and Flexor 

 carpi ulriaris ;. by its inner surface to the Flexor brevis minimi digit! and the 

 Flexor ossis metacarpi minimi digiti ; and is grooved on its outer side, for the 

 passage of the Flexor tendons into the palm of the hand. This is one of the four 

 eminences on the front of the carpus to which the anterior annular ligament is 

 attached, the others being the pisiform internally, the oblique ridge of the trape- 

 zium and the tuberosity of the scaphoid externally. The internal surface articu- 

 lates with the cuneiform by an oblong facet cut obliquely from above, downward 

 and inward. The external surface articulates with the os magnum by its upper 

 and posterior part, the remaining portion being rough, for the attachment of 

 ligaments. 



Hold the bone with the hooked process away from you, and the articular sur- 

 face, divided into two parts, for the metacarpal bones, downward. The concavity 

 of the process will be on the side to which the bone belongs. 



Articulations. With five bones : the semilunar above, the fourth and fifth 

 metacarpal below, the cuneiform internally, the os magnum externally. 



Attachment of Muscles. To three : the Flexor brevis minimi digiti, the Flexor 

 ossis metacarpi minimi digiti, the Flexor carpi ulnaris. 



The Metacarpus. 



The Metacarpal Bones are five in number: they are long, cylindrical bones, 

 presenting for examination a shaft and two extremities. 



Common Characters of the Metacarpal Bones. 



The Shaft is prismoid in form and curved longitudinally, so as to be convex in 

 the longitudinal direction behind, concave in front. It presents three surfaces: 

 two lateral and one posterior. The lateral surfaces are concave, for the attach- 

 ment of the Interossei muscles, and separated from one another by a prominent 

 anterior ridge. The posterior or dorsal surface presents in its distal half a smooth, 

 triangular, flattened area which is covered, in the recent state, by the tendons of 

 the Extensor muscles. This triangular surface is bounded by two lines, which 

 commence in small tubercles situated on the dorsal aspect on either side of the 



